1. Field of the Invention
The present invention is broadly concerned with passive fire-suppression objects which can be placed in or adjacent a confined area for the purpose of providing rapid extinguishment of fires. More particularly, the invention pertains to such fire-suppression objects, and corresponding methods of fire-suppression, wherein the suppression objects include solid polyhalon fire-suppressing material which is capable of releasing halon or halon-like gas when heated as a result of fire within a protected confined zone or area.
2. Description of the Prior Art
The halons are brominated chlorofluorocarbon compounds related to the CFC family of compounds because of their chemical structure. Certain halon compounds, particularly 1301 (trifluorobromomethane) and 1211 (bromochlorodifluoromethane) are known as very effective fire extinguishants and have very low toxicity. Accordingly, these compounds have achieved widespread use throughout the world in fire extinguishing equipment.
Beginning in about 1974, scientists began establishing a link between CFCs and stratospheric ozone depletion. Subsequent findings led to international action, culminating in the Montreal Protocol of 1987, where the world community acted to protect the stratospheric ozone layer from degradation due to CFCs and related compounds. Halons are included in the list of regulated chemicals being phased out by incremental production cutbacks. At this time, production of both halons 1301 and 1211 has been stopped. Production of halons was stopped because they are known to have long atmospheric lifetimes and release free chlorine in the stratosphere when broken down by incoming, high energy UV light. Halons also release free l bromine causing additional ozone depletion.
In response to these problems, it has been suggested to provide non-volatile precursors (NVPs) for halons wherein halon or halon-like fire extinguishing agents are trapped or tied up in a chemical matrix. When exposed to elevated temperatures caused by fire, the NVPs release halon or halon-like compounds. The advantage of such NVPs is that they are inert and thus have a zero or near-zero ozone-depletion potential. Moreover, the amount of halon or halon-like gas generated by such NVPs is significantly less than that employed in typical prior halon fire extinguishing systems and is in effect self-limiting, i.e., after a sufficient quantity of fire extinguishing gas is liberated due to the fire, the fire is extinguished and there is then insufficient heat to initiate further chemical release.
As a result of this work, a number of NVP compounds have been developed which have been shown to be effective fire extinguishants, many of which are even superior to the halons currently in use. These compounds include ethyl dibromofluoroacetate, ethyl bromodifluoroacetate, 1,4-dibromo-butane, 1-iodo-3-bromobutane, and 1,2-dibromo-1,1,2-trifluoroethane. See, Bannister et al., Recent Advances in Development of Non-Volatile Precursors NVPs! to Alternative Halon Fire Extinguishing Agents with Reduced Global Environmental Impacts, Proceedings of Halon Alternatives Technical Working Conference, 1993, incorporated by reference herein.
Additional work in this area has involved the preparation of polyhalons such as poly-1,2-dibromoethylene, polyvinyladene bromide, polyvinyl bromide, polybromotrifluoroethylene, cellulose tribromoacetate, polyvinyl tribromoacetate, polyf4-(2,2,3,3-tetrabromobutane)oxalate!. Some of these agents have been shown to have fire-suppression capabilities, although in some instances their physical properties may render them difficult to use. See, Bannister et al., Low Volatility Halon Fire Extinguishing Agents with Reduced Global Environmental Impacts, Proceedings of Halon Options Technical Working Conference, May, 1995, and Bannister et al., Low Volatility Halon Fire Extinguishing Agents with Reduced Global Environmental Impacts, Proceedings of Halon Options Technical Working Conference, May, 1996. One polyhalon, polybromotrifluoroethylene (CF.sub.2 --CFBr)n, has been shown to extinguish fire in a "wastebasket" test. However, to date the polyhalons have not been formulated into any commercially useful product.